BRIEF [O.A.] Bamberger, Johann Author: Bamberger, Johann Recipient: Haeckel, Ernst Dating: 16.02.1915
BRIEF [O.A.] Unna, P...(aul) G...(erson) Author: Unna, P...(aul) G...(erson) Recipient: Haeckel, Ernst Dating: 30.05.1915
BRIEF OHNE UMSCHLAG Sokolowsky, Alexander Author: Sokolowsky, Alexander Recipient: Haeckel, Ernst Dating: 23.12.1915